Applied sciences

Archives of Thermodynamics

Content

Archives of Thermodynamics | 2019 | vol. 40 | No 2 |

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Abstract

In this study a steady flow-field and heat transfer through a copper-water nanofluid around a circular cylinder, under the influence of both the standard thermal boundary conditions, i.e., uniform heat flux and constant wall temperature) was investigated numerically by using a finitevolume method for Reynolds numbers from the range 10–40. Furthermore, the range of nanoparticle volume fractions considered is 0–5%. The variation of the local and the average Nusselt numbers with Reynolds number, and volume fractions are presented for the range of conditions. The average Nusselt number is found to increase with increasing the nanoparticle volume fractions.
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Authors and Affiliations

Kamel Korib
Nabila Ihaddadene
Rafik Bouakkaz
Yacine Khelili
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Abstract

Experimental research has been carried out for four individual heat exchanger constructions, i.e., plain double tube, turbulized double tube, plain U-bend and U-bend with turbulator. Tests were made for the water-water system. The study covered a wide measuring range, i.e., Re = 800–9000 – on the shell side, for a constant cold water temperature of 9 ◦C and hot water of 50 ◦C. The heat exchangers were made from copper tubes with external diameter of 10 mm and 18 mm respectively and wall thickness of 1 mm. The helicoidal vortex generator was made from brass wire with a diameter of 2.4 mm, coil diameter of 13 mm and pitch of 11 mm. For these geometries, the values of pressure drop, heat flux and heat transfer coefficient were determined. Wire coil turbulator increased the heat transfer coefficient (HTC) over 100% and pressure drop up by 100%. The comparison of heat transfer efficiency was performed based on the number of transfer units-effectivenes (NTU-ε) method. The modified construction achieved a similar efficiency. Economic analysis of wire coil turbulator was made to validate its use in the system. It showed that a coiled wire turbulator can greatly decrease the investment cost of the double tube heat exchanger while maintaining transferred heat at a constant level.
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Authors and Affiliations

Rafał Andrzejczyk
Tomasz Muszyński
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Abstract

A Stirling cycle was developed by Rallis considering the adiabatic behaviour instead of isothermal behaviour of working fluid inside the expansion/compression volume, since the isothermal processes are very difficult to be realised in actual practice due to irreversibilities. In order to increase the performance of Rallis Stirling cycle engine, two modified versions of Rallis Stirling cycle engine model have been proposed and developed, called as Rallis modified Stirling cycle engine (RMSE). In this paper, the thermodynamic analysis of the developed models have been carried out and the simulated results are compared with the Rallis ideal model of Stirling cycle engine, as this model describes more accurately the thermodynamic cycle of practical Stirling machines. The results reveal the fact that the thermal efficiency of RMSE I model is enhanced by 38.06% and that of RMSE II model by 48.42%, whereas the power output is increased by 58.05% and 78.19% in case of RMSE I and RMSE II model respectively, when compared with the Rallis ideal adiabatic model of Stirling engine.
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Authors and Affiliations

Ravi Kant Ranjan
Suresh Kant Verma
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Abstract

In the present discussion, the plane strain deformation due to laser pulse heating in a thermoelastic microelongated solid has been discussed. The analytic expressions for displacement component, force stress, temperature distribution and micro-elongation have been derived. The effect of pulse rise time and micro-elongation on the derived components have been depicted graphically.
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Authors and Affiliations

Praveen Ailawalia
Sunil Kumar Sachdeva
Devinder Singh Pathania
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Abstract

In this work, actual operating data for Sabiya combined cycle power plant located in Kuwait were used to conduct the performance evaluation based on the energetic and exergetic analysis. The proposed system consist of an advanced gas turbine engines, with two triple pressure reheat heat recovery steam generator, and one steam turbine. Three types of primary movers were selected carefully, in order to cover different types, sizes and technologies. The movers are gas turbine engine frame 9FA, LM6000 and GT26. The proposed models have been developed using specialised software and validated with the manufacturer’s data featuring a high level of compatibility. The performance of a combined cycle power plant was investigated for different operating conditions. The result shows that the highest exergy destruction takes place in 9FA engine due to high irreversibility in combustion chamber because of low-pressure ratio, which causes low inlet temperature of compressed air to the combustion chamber. The 9FA engine also has the highest exergy loss due to high exhaust gases temperature, which is caused high useful work from a steam turbine. The GT26-reheat gas turbine engine constitute the best choose as primary mover due to low waste exergy, which is equal to 43.93% whereas 9FA and LM6000 equal to 47.27% and 45.17%, respectively. LM6000 aeroderivative gas turbine is considered the second best choice but the combined cycle power plant will consist of a large number of engines compared to other industrial gas turbine engine, and that may increase the number of auxiliary equipment, capital and maintenance cost.
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Authors and Affiliations

Abdulrahman Almutairi
Hamad Alhajeri
Abdulrahman Alenezi
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Abstract

In present article a mathematical model of arc shape wire roughened solar air heater, on the basis of energy and exergy output rates, entropy generation rate and augmentation entropy generation number, has been developed. A parametric study leading to entropy generation minimization has also been performed. In the analysis the geometric and operating parameters which have been considered as variable are: inlet air temperature, duct depth, collector width to duct depth ratio, mass flow rate per unit collector area, and temperature rise parameter . Results have been presented to see the effects of these values on the energy and exergy output rates of the roughened solar air heater. Effect of different values of wire rib roughness parameters on entropy generation has also been presented. Finally, design curves and optimization for different rib roughness parameters on the basis of minimum entropy generation number with temperature rise parameter, have been presented and optimum values also have been found out 0.004 to 0.010 (Km2)/W. The entropy generation rate obtained for the system, in the present work has been compared with those obtained for solar air heater with different roughness geometries on absorber plates available in the literature for common roughness parameters and operating parameters which validate the present results.
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Authors and Affiliations

Mukesh Kumar Sahu
Radha Krishna Prasad
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Abstract

The paper presents a numerical model for analyzing vaporliquid equilibrium of ternary (three-component) system at high pressures. The gas-phase non-idealities and solubility of gas in liquid are considered in the numerical model. The model is useful for studies involving evaporation of liquid at different pressure and temperature conditions, where the interface liquid and vapor compositions are required. At high ambient pressures, ambient gases dissolve into the liquid. Thus, even a single component liquid fuel evaporating in a high pressure ambient gas, effectively behaves like a two-component liquid system. This study considers a ternary system. The numerical model has been validated against the experimental data available in literature. The validated model is used to study the solubility of ambient gas in a binary liquid mixture at high pressures. The effects of pressure, temperature and liquid phase composition on the solubility of gas in liquid have been studied systematically.
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Authors and Affiliations

Saroj Ray
V.V. Sree Harsha
Vasudevan Raghavan
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Abstract

The conditions of efficient use of heat pumps in air conditioning systems are considered in order to ensure the established temperature and relative humidity of air in premises with the removal of excess moisture in the warm or hot periods of the year. For this purpose, a thermodynamic analysis of heat pump air conditioning schemes with exhaust air recirculation through a condenser and through a heat pump evaporator has been carried out. To determine the potential capabilities of such schemes to maintain comfortable conditions in the production room, a numerical analysis of their operating parameters, depending on the temperature and relative humidity of external atmospheric air, was performed. It has been shown that recirculation of exhaust air through the heat pump evaporator allows to maintain the given conditions in the room in a wider range of parameters of external atmospheric air. In addition, it has been shown that such a scheme requires less specific energy consumption for the operation of heat pump, which means that it is more efficient.
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Authors and Affiliations

Mikhail Bezrodny
Natalia Prytula
Maria Tsvietkova

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